Apparatus and method for exposing a substrate to UV radiation using a reflector having both elliptical and parabolic reflective sections

ABSTRACT

Embodiments of the invention relate generally to an ultraviolet (UV) cure chamber for curing a dielectric material disposed on a substrate and to methods of curing dielectric materials using UV radiation. A substrate processing tool according to one embodiment comprises a body defining a substrate processing region; a substrate support adapted to support a substrate within the substrate processing region; an ultraviolet radiation lamp spaced apart from the substrate support, the lamp configured to transmit ultraviolet radiation to a substrate positioned on the substrate support; and a motor operatively coupled to rotate at least one of the ultraviolet radiation lamp or substrate support at least 180 degrees relative to each other. The substrate processing tool may further comprise one or more reflectors adapted to generate a flood pattern of ultraviolet radiation over the substrate that has complementary high and low intensity areas which combine to generate a substantially uniform irradiance pattern if rotated. Other embodiments are also disclosed.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.60/783,421, filed Mar. 17, 2006; U.S. Provisional Application No.60/816,660, filed Jun. 26, 2006; U.S. Provisional Application No.60/816,723, filed Jun. 26, 2006; and U.S. Provisional Application No.60/886,906, filed Jan. 26, 2007 are herein incorporated herein byreference in their entirety.

This application is related to U.S. application Ser. No. 11/686,881,filed Mar. 15, 2007; and to U.S. application Ser. No. 11/686,878, filedMar. 15, 2007; and to U.S. application Ser. No. 11/686,900, filed Mar.15, 2007; and to U.S. application Ser. No. 11/686,897, filed Mar. 15,2007. Each of the applications listed above are assigned to AppliedMaterials, Inc., the assignee of the present invention and are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

Materials such as silicon oxide (SiO_(x)), silicon carbide (SiC) andcarbon doped silicon oxide (SiOC_(x)) films find widespread use in thefabrication of semiconductor devices. One approach for forming suchsilicon-containing films on a semiconductor substrate is through theprocess of chemical vapor deposition (CVD) within a chamber. Forexample, chemical reaction between a silicon supplying source and anoxygen supplying source may result in deposition of solid phase siliconoxide on top of a semiconductor substrate positioned within a CVDchamber. As another example, silicon carbide and carbon-doped siliconoxide films may be formed from a CVD reaction that includes anorganosilane source including at least one Si—C bond.

Water is often a by-product of the CVD reaction of organosiliconcompounds. As such, water can be physically absorbed into the films asmoisture or incorporated into the deposited film as Si—OH chemical bond.Either of these forms of water incorporation are generally undesirable.Accordingly, undesirable chemical bonds and compounds such as water arepreferably removed from a deposited carbon-containing film. Also, insome particular CVD processes, thermally unstable organic fragments ofsacrificial materials need to be removed.

One common method used to address such issues is a conventional thermalanneal. The energy from such an anneal replaces unstable, undesirablechemical bonds with more stable bonds characteristic of an ordered filmthereby increasing the density of the film. Conventional thermal annealsteps are generally of relatively long duration (e.g., often between 30min to 2 hrs.) and thus consume significant processing time and slowdown the overall fabrication process.

Another technique to address these issues utilizes ultraviolet radiationto aid in the post treatment of CVD silicon oxide, silicon carbide andcarbon-doped silicon oxide films. For example, U.S. Pat. Nos. 6,566,278and 6,614,181, both to Applied Materials, Inc. and incorporated byreference herein in their entirety, describe the use of UV light forpost treatment of CVD carbon-doped silicon oxide films. The use of UVradiation for curing and densifying CVD films can reduce the overallthermal budget of an individual wafer and speed up the fabricationprocess. A number of various UV curing systems have been developed whichcan be used to effectively cure films deposited on substrates. Oneexample of such is described in U.S. application Ser. No. 11/124,908,filed May 9, 2005, entitled “High Efficiency UV Curing System,” which isassigned to Applied Materials and incorporated herein by reference forall purposes.

Despite the development of various UV curing chambers, furtherimprovements in this important technology area are continuously beingsought.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the invention relate generally to an ultraviolet (UV)cure chamber for curing a dielectric material disposed on a substrateand to methods of curing dielectric materials using UV radiation.

A substrate processing tool according to one embodiment comprises a bodydefining a substrate processing region; a substrate support adapted tosupport a substrate within the substrate processing region; anultraviolet radiation lamp spaced apart from the substrate support, thelamp configured to transmit ultraviolet radiation to a substratepositioned on the substrate support; and a motor operatively coupled torotate at least one of the ultraviolet radiation lamp or substratesupport at least 180 degrees relative to each other. The substrateprocessing tool may further comprise one or more reflectors adapted togenerate a flood pattern of ultraviolet radiation over the substratethat has complementary high and low intensity areas which combine togenerate a substantially uniform irradiance pattern if rotated.

A substrate processing tool according to another embodiment of theinvention comprises a body defining a substrate processing region; asubstrate support adapted to support a substrate within the substrateprocessing region; an ultraviolet (UV) radiation lamp spaced apart fromthe substrate support and configured to generate and transmitultraviolet radiation to a substrate positioned on the substratesupport, the UV radiation lamp comprising a source of UV radiation and aprimary reflector partially surrounding the source of UV radiation, anda secondary reflector positioned between the primary reflector and thesubstrate support, the secondary reflector adapted to redirectultraviolet radiation that would otherwise not contact the substratetowards the substrate. In some embodiments the secondary reflectorcomprises an upper portion and a lower portion each of which includesopposing longitudinal surfaces that meet at a vertex traversing a lengthof the longitudinal surfaces and opposing transverse surfaces extendingbetween ends of the longitudinal surfaces.

A substrate processing tool according to another embodiment of theinvention comprises a body defining a substrate processing region; asubstrate support adapted to support a substrate within the substrateprocessing region; and a first UV lamp spaced apart from the substratesupport and configured to transmit UV radiation to a substratepositioned on the substrate support, the first UV lamp comprising afirst UV radiation source and a first reflector partially surroundingthe first UV radiation source, the first reflector having opposing innerand outer reflective panels, the inner reflective panel having a firstreflective surface and the outer reflective panel having a secondreflective surface that is asymmetric to the first reflective surface.Some embodiments further include a second UV lamp spaced apart from thesubstrate support and configured to transmit UV radiation to a substratepositioned on the substrate support, the second UV lamp comprising asecond UV radiation source and a second reflector partially surroundingthe second UV radiation source, the second reflector opposing inner andouter reflective panels, the inner reflective panel having a thirdreflective surface and the outer reflective panel having a fourthreflective surface that is asymmetric to the third reflective surface.

A substrate processing tool according to another embodiment of theinvention comprises a body defining a substrate processing region; asubstrate support adapted to support a substrate within the substrateprocessing region; an ultraviolet (UV) radiation lamp spaced apart fromthe substrate support and configured to generate and transmitultraviolet radiation to a substrate positioned on the substratesupport, the UV radiation lamp comprising a source of UV radiation and aprimary reflector partially surrounding the source of UV radiation; asecondary reflector positioned between the primary reflector and thesubstrate support configured to reduce light loss outside the substrate,the secondary reflector having an inner and outer surface and at leastone hole traversing the reflector from the inner surface to the outersurface; and a light detector positioned to receive UV radiation lightgenerated by the UV radiation lamp transmitted through the at least onehole.

A substrate processing tool according to another embodiment of theinvention comprises a body defining a substrate processing region; asubstrate support adapted to support a substrate within the substrateprocessing region; an ultraviolet (UV) radiation lamp spaced apart fromthe substrate support and configured to generate and transmitultraviolet radiation to a substrate positioned on the substratesupport, the UV radiation lamp comprising a source of UV radiation and aprimary reflector partially surrounding the source of UV radiation; asecondary reflector positioned between the primary reflector and thesubstrate support configured to reduce light loss outside the substrate,the secondary reflector having an inner and outer surface and at leastone hole traversing the reflector from the inner surface to the outersurface; and a light detector positioned to receive UV radiation lightgenerated by the UV radiation lamp transmitted through the at least onehole.

A substrate processing tool according to another embodiment of theinvention comprises a body defining a substrate processing region; asubstrate support adapted to support a substrate within the substrateprocessing region; and an ultraviolet (UV) radiation lamp spaced apartfrom the substrate support and configured to generate and transmitultraviolet radiation to a substrate positioned on the substratesupport, the UV radiation lamp comprising a source of UV radiation and aprimary reflector partially surrounding the source of UV radiation, theprimary reflector having a reflective surface that includes at least oneparabolic section and at least one elliptical section. In one embodimentthe primary reflector comprises inner and outer reflective panels eachof which has a reflective surface that includes at least one parabolicsection and at least one elliptical section.

A method of curing a layer of dielectric material formed over asubstrate according to one embodiment comprises placing the substratehaving the dielectric material formed thereon on a substrate support ina substrate processing chamber; and exposing the substrate toultraviolet radiation from a source of ultraviolet radiation that isspaced apart from the substrate support while rotating either theultraviolet radiation source and/or substrate during the exposing step.The exposing step in some embodiments includes generating asubstantially circular flood pattern having complementary high and lowintensity areas which combine to generate a substantially uniformirradiance pattern during rotation during the exposing step.

A method of curing a layer of dielectric material formed over asubstrate according to another embodiment comprises placing thesubstrate having the dielectric material formed thereon on a substratesupport in a substrate processing chamber; exposing the substrate toultraviolet radiation by generating a substantially rectangular floodpattern of UV radiation with a UV source and primary reflector andreshaping the substantially rectangular flood pattern into asubstantially circular flood pattern of UV radiation with a secondaryreflector positioned between the primary reflector and the substratesupport.

A method of curing a layer of dielectric material formed over asubstrate, the method comprising placing the substrate having thedielectric material formed thereon on a substrate support in a substrateprocessing chamber; and exposing the substrate to UV radiation bygenerating the radiation with an elongated UV source and redirecting theUV radiation generated by the UV source with first and second reflectivesurfaces that partially surround the radiation source and are asymmetricto each other. A method of curing a layer of dielectric material formedover a substrate according to another embodiment comprises placing thesubstrate having the dielectric material formed thereon on a substratesupport in a substrate processing chamber; and exposing the substrate toUV radiation by (i) generating the radiation with first and second UVsources, (ii) redirecting UV radiation generated by the first UV sourcewith first and second reflective surfaces that are asymmetric to eachother and combine to concentrate the UV radiation on a first half of thesubstrate, and (iii) redirecting UV radiation generated by the second UVsource with third and fourth reflectors that are asymmetric to eachother and combine to concentrate the UV radiation on a second half ofthe substrate opposite the first half.

A method of curing a layer of dielectric material formed over asubstrate according to another embodiment comprises placing thesubstrate having the dielectric material formed thereon on a substratesupport in a substrate processing chamber; and exposing the substrate toUV radiation by generating the radiation with an elongated UV source andredirecting the UV radiation generated by the UV source with opposingfirst and second reflective surfaces that partially surround theradiation source where at least one of the opposing first and secondsurfaces includes at least one parabolic section and at least oneelliptical section.

These and other embodiments of the present invention, as well as itsadvantages and features, are described in more detail in conjunctionwith the text below and attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a prior art UV lamp that illustrativelydepicts an approximate irradiance level of light generated by the lampover an exposure area;

FIG. 2 is a simplified depiction of the primary irradiance pattern of aprior art UV lamp at different lamp-to-wafer distances;

FIG. 3 is cross-sectional perspective view of a UV lamp module thatincludes a secondary reflector according to one embodiment of thepresent invention;

FIG. 4 is a simplified depiction of the irradiance pattern of UV lampmodule 30 according to an embodiment of the invention;

FIG. 5 is a top perspective view of the secondary reflector 42 depictedin FIG. 3;

FIG. 6A is a simplified cross-sectional illustration along an axistransverse to UV lamp module 30 of several reflection paths for UVradiation generated by a UV lamp module according to an embodiment ofthe present invention;

FIG. 6B is a simplified cross-sectional illustration along an axislongitudinal to UV lamp module 30 of several reflection paths for UVradiation generated by a UV lamp module according to an embodiment ofthe present invention;

FIGS. 7A-7B are a simplified cross-sectional views of primary reflector36 shown in FIG. 3 depicting selected reflective paths generated by thereflector according to one embodiment of the invention;

FIG. 7C includes a simplified perspective, cross-sectional and partialexploded view of a primary reflector that includes a reflective surfacehaving both parabolic and elliptical shaped sections according to oneembodiment of the invention;

FIG. 7D is a simplified cross-sectional view showing the reflectivepattern of a parabolic section 136 a of the reflector shown in FIG. 7C;

FIG. 7E is a simplified cross-sectional view showing the reflectivepattern of elliptical sections 136 b-136 d of the reflector shown inFIG. 7C;

FIG. 8 is a simplified plan view of a semiconductor processing system inwhich embodiments of the invention may be incorporated;

FIG. 9 is a simplified perspective view of a tandem process chamber 106shown in FIG. 8 configured for UV curing according to one embodiment ofthe invention;

FIG. 10 is a perspective view of secondary reflector 40 attached to adisc 212 that enables the reflector and UV lamp to be rotated withrespect to the substrate being exposed to UV radiation according to oneembodiment of the invention;

FIG. 11A graphically depicts the irradiance pattern of UV lamp module 30according to an embodiment of the invention;

FIG. 11B depicts actual radiation levels shown in FIG. 11A along bothaxis 69 and axis 70;

FIG. 11C graphically depicts the irradiance pattern of UV lamp module 30when rotated during UV exposure according to an embodiment of theinvention;

FIG. 11D depicts actual radiation levels shown in FIG. 11C along axis86;

FIGS. 12A-C are simplified top plan drawings depicting drive mechanismsfor rotating dual UV lamp modules, such as module 30 shown in FIG. 3,according to various embodiments of the invention; and

FIG. 13 is a simplified cross-sectional view of the tandem processchamber 106 illustrated in FIG. 8.

FIG. 14 is a simplified cross-sectional view of a dual lamp chamberaccording to one embodiment of the present invention;

FIG. 15 is a bottom plan view of lamps 410 and 412 depicted in FIG. 14;

FIGS. 16-18 graphically depict the irradiance pattern of portions of UVcure system 400 depicted in FIG. 14;

FIG. 19 is a simplified cross-sectional view of a dual lamp chamberaccording to another embodiment of the present invention;

FIG. 20 is a simplified perspective view of secondary reflector 440shown in FIG. 14 that illustrates a possible location for light pipesthat independently monitor each of the UV bulbs and primary reflectorsof UV cure system 400 according to one embodiment;

FIG. 21 is a simplified perspective view of secondary reflector 440including light pipes to independently monitor each of the primaryreflectors and UV bulbs of UV cure system 400 according to oneembodiment; and

FIGS. 22A and 22B are simplified perspective views of a portion of asecondary reflector according to another embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a perspective view of a prior art microwave UV lamp 10 thatillustratively depicts an irradiance level of radiation generated by thelamp over a substantially rectangular exposure area. Lamp 10 includes anelongated UV bulb 12 mounted within a housing 14. Housing 14 includes areflector 16 that faces UV bulb 12 and directs UV radiation into anirradiance pattern 18 over a substrate 20. Reflector 16 is placed insidea resonant cavity, which limits the size and shape of the reflector.

While reflector 16 reflects the majority of radiation (within selectedwavelengths) that strikes its surface within flood pattern 18, someradiation escapes the reflector surface and falls outside the boundariesof pattern 18. An example of such radiation is illustrated in FIG. 1 byradiation path 15. The intensity of radiation generated by lamp 10 bothwithin and outside flood pattern 18 is illustrated conceptually (in asimplified manner) in bottom portion 22 of FIG. 1. As shown in bottomportion 22, the intensity of UV radiation generated by lamp 10 isessentially (or close to) uniform within the boundary of flood pattern18 (flat line 23). Some radiation falls outside of region 18 in anamount that decreases with the distance from the boundary as shown bysloped line 24 until the radiation level reaches zero as shown by line25.

UV lamp modules similar to lamp 10 have been used to cure dielectricmaterials deposited over substantially round semiconductor substrates.One problem with such use, however, is that because of its shape, inorder to expose the entire semiconductor substrate, the substantiallyrectangular exposure pattern generated by lamp 10 necessarily produces acertain amount of radiation that is outside the boundaries of thesubstrate.

This problem is illustrated graphically in FIG. 2, which depicts theirradiance outline at different wafer-to-lamp distances. As shown inFIG. 2, if a round substrate 28 is positioned relatively close to lamp10 (position A), portions of the substrate (e.g., portions 28 a) falloutside the irradiance pattern 18. Moving the substrate further from UVlamp 10 (position B) can result in the entire substrate falling withinthe irradiance pattern but will also result in a substantial portion ofradiation in the primary irradiance pattern falling outside theboundaries of the substrate.

Another problem with such use is that even where the edge of irradiancepattern 18 is matched with an outer edge of the substrate, radiationthat corresponds to sloped line 24 (FIG. 1) would also fall outside theboundary of the substrate. Generally it is desirable to concentrate asmuch uniform UV radiation over the surface of the substantially circularsemiconductor substrate as possible. The problems described above inconjunction with a prior art lamp run counter to such an ideal exposure.

FIG. 3 is cross-sectional perspective view of a UV lamp module 30according to an embodiment of the present invention that includes asecondary reflector 40 designed to increase the intensity of energydistributed to a substrate. Lamp module 30 also includes a UV lamp 32(e.g., a high power mercury microwave lamp) having an elongated UV bulb34 partially surrounded by a primary reflector 36. As shown in FIG. 3,secondary reflector 40 is positioned between UV lamp 32 and asemiconductor substrate 50. The lower edge of the reflector has adiameter that is smaller than a diameter of the substrate so there is nooptical gap between the secondary reflector and the outside diameter ofthe substrate as viewed from the direction of the lamp.

A UV transparent window 48 (e.g., a quartz window) is positioned betweenlamp 32 and substrate 50 and a small gap exists between the bottom ofthe secondary reflector and the UV transparent window to allow for airflow around the secondary reflector. In one embodiment the distancebetween the upper surface of substrate 50 that is exposed to UVradiation and the bottom of secondary reflector 40, which includes thethickness of window 48, is approximately 1.5 inches. Because of thesmaller diameter of the lower reflector edge as compared to thesubstrate diameter, loss of light to the substrate is minimal despitethe spacing.

The secondary reflector has a channeling effect reflecting UV radiationthat would otherwise fall outside the boundary of the primaryreflector's flood pattern (e.g., radiation 15 in FIG. 1) so that suchradiation impinges upon the substrate being treated thus increasing theintensity of the energy distributed to the substrate. As shown in FIG.4, secondary reflector 40 alters the flood pattern of UV lamp 32 from asubstantially rectangular area (e.g., as shown in FIG. 1) to asubstantially circular shape 49 that corresponds to the substantiallycircular semiconductor substrate being exposed.

Referring now to both FIGS. 3 and 5, which is a top perspective view ofsecondary reflector 40 depicted in FIG. 3, the secondary reflectorincludes an upper portion 41 and a lower portion 42 which meet at avertex 43 that extends around the interior perimeter of reflector 40.Upper portion 41 includes a semicircular cut-out 46 to allowunobstructed flow of lamp cooling air. Upper portion 41 also includestwo opposing and generally inward sloping (from the top) longitudinalsurfaces 41 a and two opposing transverse surfaces 41 b. Transversesurfaces 41 b are generally vertical and have a convex surface along thetransverse direction. Longitudinal surfaces 41 a are generally concavealong the longitudinal direction.

Lower portion 42, which is positioned directly below upper portion 41,includes two opposing and generally outward sloping (from the top)surfaces 42 a and two opposing generally outward sloping transversesurfaces 42 b. In the embodiment shown in FIGS. 3 and 5, surfaces 42 bare at a reduced angle (relative to the vertical) than surfaces 42 a.Longitudinal surfaces 42 a are generally concave along the longitudinaldirection while surfaces 42 b are generally convex (with a notableexception being in corners 44 where the lower portion of surface 42 ameets the lower portion of surface 42 b) along the transverse direction.

As evident from FIGS. 3 and 5, secondary reflector 40 represents acomplex shape that can be customized to a particular UV radiation sourceand primary reflector. Secondary reflector 40 can also be customized (inconjunction with primary reflectors 36 when used) to particularirradiance profiles and uniformity levels depending on the requirementsof an application. For example, in some embodiments reflector 40 can bedesigned to generate an edge high irradiance profile in order tocompensate for a heater thermal profile that is center high. Also,secondary reflector 40 will generally be designed to generate differentirradiation patterns depending on whether it is used with a stationaryor rotational lamp as discussed below.

The inventors designed the embodiment shown in FIGS. 3 and 5 using acommercially available Monte Carlo raytracing simulation program,TracePro by Lambda Research Corporation. The inventors arrived at thefinal optimized design for the secondary reflector using an iterativeprocess that simulated one million rays generated by a radiation source.Persons of skill in the art will recognize that a variety of differentsimulation programs and other techniques can be employed to derive aparticular secondary reflector that is appropriate for a particular UVradiation source and primary reflector pairing.

In one embodiment secondary reflector 40 is fabricated from fourseparate machined aluminum pieces 40 a, 40 b, 40 c and 40 d where theinner surfaces of pieces 40 a and 40 c define opposing surfaces 41 a andopposing surfaces 42 a, and the inner surfaces of pieces 40 b and 40 ddefine opposing surfaces 41 b and opposing surfaces 42 b. Each ofsurfaces 41 a, 41 b, 42 a and 42 b preferably includes an opticallysmooth finish and can optionally be coated with a dichroic coatingsimilar to that described below with respect to the primary reflector.In other embodiments secondary reflector 40 can be made up of more orfewer than four pieces and in some embodiments secondary reflector 40can be machined from a single block of material. In another embodimentsecondary reflector 40 is made from quartz having inner reflectivesurfaces coated with a dichroic coating.

FIG. 6A is a simplified cross-sectional illustration along a transverseaxis of UV lamp module 30 showing several reflection paths for UVradiation according to an embodiment of the present invention. FIG. 6Bis a simplified cross-sectional illustration along a longitudinal axisof UV lamp module 30 illustrating additional reflection paths for UVradiation according to an embodiment of the present invention. As shownin FIGS. 6A and 6B, secondary reflector 40 allows substantially all UVradiation generated by bulb 34 to be directed towards and impinge upon asubstrate 50 positioned below the UV lamp module. In some embodiments aquartz window or similarly UV transparent window, which is not shown ineither FIG. 6A or 6B for ease of illustration, may be present betweenthe lower surface of module 30 and substrate 50 as described above withrespect to FIG. 3.

FIG. 6A shows radiation from lamp 34 impinging upon substrate 50 by oneof three different exemplary paths: a path 45 a that strikes substrate50 directly without being reflected from either primary reflector 36 orsecondary reflector 40, a path 45 b that strikes substrate 50 afterbeing reflected by upper portion 41 a of secondary reflector 40 and apath 45 c that strikes substrate 50 after being reflected by lowerportion 42 a of reflector 40. FIG. 6B shows radiation from lamp 34impinging upon substrate 50 by one of several additional exemplarypaths: a second path 45 a that strikes substrate 50 directly withoutbeing reflected off of either primary reflector 36 or secondaryreflector 40, a path 45 d that strikes substrate 50 after beingreflected by upper portion 41 b of secondary reflector 40 and a path 45e that strikes substrate 50 after being reflected by lower portion 42 bof reflector 40. It is to be understood that the paths 45 a to 45 eshown in FIGS. 6A and 6B are exemplary paths only and that many otherreflection paths will be generated by secondary reflector 40 includingsome relatively complicated paths in which radiation is reflected uponmultiple points of the secondary reflector as, for example, may be thecase where radiation first contacts upper portion 41 in an area near thecorner where parts 40 a and 40 d intersect.

Referring back to FIG. 3, the secondary reflector employed in someembodiments of the present invention can be employed with any of anumber of different UV lamps. In the embodiment illustrated in FIG. 3,UV lamp 32 includes a single elongated UV bulb 34 and a pair of interiorreflective panels 36 positioned in an opposing and facing orientationspaced from bulb 34. Reflector 36 is mounted in a spaced relationshipwith respect to bulb 34. Bulb 34 and reflective panels are bothpositioned inside an elongated resonant cavity (which for ease ofillustration, is not shown). Each reflective panel 36 extendslongitudinally along the length of the UV bulb and includes a concaveinner surface that has an optically smooth finish. Note, that FIG. 3shows panels 36 as a pair of separate unconnected panels for ease ofillustration, embodiments of the invention are not limited to such. Insome embodiments, reflector panels 36 are connected as a single U-shapedcomponent that may include holes or apertures above bulb 34 to allow airflow across the bulb.

Reflective panels 36 affect the irradiance profile across the lamp andare designed to compensate for direct light non-uniformity (irradiancealong the lamp is a function of distance from the center of the lamp).In one embodiment in which a single UV lamp 32 is used to irradiate asubstrate, the pair of reflective panels 36 have opposing symmetricreflective surfaces. In some embodiments of the invention, for examplewhen two or more UV lamps 32 are used to irradiate a substrate,asymmetric pairs of reflective panels 36 in individual UV lamps are usedas described more fully below. Reflective panels 36 may be eitherelliptical or parabolic reflectors or include a combination of bothelliptical and parabolic reflective portions. The inventors have foundthat elliptical reflectors can fit in a smaller resonant cavity for thesame width of light beam than parabolic reflectors and can also achievesuperior light uniformity as compared to parabolic reflectors. Theinventors have also found, however, that reflective panels having bothelliptical and parabolic sections allow for the greatest flexibility increating reflection patterns tailored to an applications particularneeds as described more fully below.

As used herein, an elliptical reflector need not have a true or perfectellipse shape. Instead, a reflector that has a partial orsemi-elliptical shape that does not have a clearly defined focal pointis also referred to as an elliptical reflector. Similarly, a parabolicreflector need not have a true or perfect parabolic shape. Instead, areflector that has a partial or semi-parabolic shape that reflects raysthat are not exactly parallel is also referred to as a parabolicreflector.

Referring back to FIG. 3, the interior surface of each reflector panel36 is defined by a cast quartz lining coated with a dichroic coating.The quartz lining reflects UV radiation emitted from UV bulb 34. Thedichroic coating comprises a periodic multilayer film composed ofdiverse dielectric materials having alternating high and low refractiveindices that does not reflect all of the damaging heat-generatinginfrared radiation. Thus, reflector panels 36 function as a cold mirror.A UV lamp 32 suitable for use with the present invention can becommercially purchased from, for example, Nordson Corporation inWestlake, Ohio or by Miltec UV in Stevenson, Md. In one embodiment, UVlamp 32 includes a single elongated UV H+ bulb from Miltec. In otherembodiments, UV lamp 32 may include an elongated UV source formed fromtwo or more separate elongated bulbs, any array of UV bulbs or otherconfiguration. Embodiments of the invention are not limited to aparticular UV lamp or bulb type.

In some embodiments of the invention, reflective panels 36 are designed(in conjunction with secondary reflector 40 when a secondary reflectoris employed) to create an irradiance pattern that is tailored to aparticular application. For example, in an application that rotates theUV lamp with respect to the substrate during the treatment process,reflective panels 36 can be designed to generate an irradiance profilehaving complementary high and low intensity areas such that when thesubstrate is rotated the complementary areas compensate for each otherto create a desired uniform irradiance exposure as described withrespect to FIGS. 11A-D. Other applications may employ an exposurepattern that compensates for non-uniform properties in an as-depositedfilm in order to generate a final, cured film having improveduniformity. For example, in an application in which an as-deposited filmis center thick (i.e., a film that has a thickness in the center of thesubstrate that is greater than its thickness near the periphery of thesubstrate), reflective panels 36 can be tailored to generate anirradiance pattern that has a higher intensity in the center of thesubstrate corresponding to the area of greater deposition. Similarly, inan application where it is known that a particular region of a depositedfilm has more volatile labile species than other regions, reflectivepanels can be tailored to generate an irradiance pattern that has ahigher intensity in the area(s) of the substrate corresponding to thegreater labile species.

In one particular embodiment employing elliptical reflector panels 36,the profile of the interior surfaces of panels 36 is generated bydividing rays emitted from UV bulb 34 into equal angular sections withinthe space dictated by the resonant cavity where each angular sectionrepresents the same amount of energy emitted by bulb 34. Such anembodiment is illustrated in FIG. 7 a where reflector sections 36 a-36 kof an elliptical reflector 36 are shown. Section 36 a is designed toreflect UV radiation towards the center of the substrate. Eachsuccessive section 36 b-36 k is then designed to reflect UV radiationjust outside the previous section as illustrated in FIG. 7 b wheresections 36 a-36 k are shown to redirect UV radiation to respectiveportions 50 a-50 k of the substrate 50. The length of each interval 50a-50 k is a function of the distance between the lamp and substrate, theray incidence angle, the direct light profile and the reflectioncoefficient. A smooth continuous elliptical profile, such as that shownin FIGS. 7A and 7B is less sensitive to reflector surface imperfectionsand reflector alignment accuracy. While FIGS. 7A and 7B illustratereflector panel 36 being divided into eleven different sections, oneembodiment of the invention divides panel 36 into forty equal angularsections.

In another embodiment each reflector 36 includes one or more parabolicshaped sections and one or more elliptical shaped sections. FIG. 7Cillustrates such a combinational parabolic and elliptical reflector 136.A UV lamp 32 may include inner and outer elliptical reflectors 136arranged around an elongated bulb 34. Furthermore, inner and outerreflectors 136 may be asymmetrically shaped in order to moreparticularly tailor the irradiance profile to a particular application.

FIG. 7C includes a perspective view of reflector 136 on the left portionof the figure, a cross-sectional view of reflector 136 in the middle andan exploded cross-sectional view of portions A1 and A2 of reflector 136on the far right. As shown in FIG. 7C, reflector 136 includes a singleparabolic section 136 a and multiple elliptical sections 136 b, 136 cand 136 d which form a wave like surface as shown in the exploded viewof portion A2. Parabolic section 136 a reflects radiation to a selectedarea on substrate 50 as shown in FIG. 7D. Elliptical sections 136 b-136d reflect radiation to a different selected area of substrate 50 asshown in FIG. 7E (note that direct rays are not shown in either of FIG.7D or 7E for clarity). Each reflector 136 is designed in combinationwith UV bulbs 34 and secondary reflector 40 taking into account whetheror not the UV lamp module and/or substrate is rotated during the cureprocess to generate a pattern that provides a high intensity yet highlyuniform exposure on substrate 50. Other embodiments may include adifferent number of parabolic and/or elliptical reflector sections thanthose of reflector 136.

FIG. 8 is a simplified plan view of a semiconductor processing system100 in which embodiments of the invention may be incorporated. System100 illustrates one embodiment of a Producer™ processing system,commercially available from Applied Materials, Inc., of Santa Clara,Calif. Processing system 100 is a self-contained system having thenecessary processing utilities supported on a mainframe structure 101.Processing system 100 generally includes a front end staging area 102where substrate cassettes 109 are supported and substrates are loadedinto and unloaded from a loadlock chamber 112, a transfer chamber 111housing a substrate handler 113, a series of tandem process chambers 106mounted on the transfer chamber 111 and a back end 138 which houses thesupport utilities needed for operation of system 100, such as a gaspanel 103 and a power distribution panel 105.

Each of the tandem process chambers 106 includes two processing regionsfor processing the substrates (see, FIG. 13). The two processing regionsshare a common supply of gases, common pressure control and commonprocess gas exhaust/pumping system. Modular design of the system enablesrapid conversion from any one configuration to any other. Thearrangement and combination of chambers may be altered for purposes ofperforming specific process steps. Any of the tandem process chambers106 can include a lid according to aspects of the invention as describedbelow that includes one or more ultraviolet (UV) lamps for use in a cureprocess of a low K material on the substrate and/or in a chamber cleanprocess. In one embodiment, all three of the tandem process chambers 106have UV lamps and are configured as UV curing chambers to run inparallel for maximum throughput.

In an alternative embodiment where not all of the tandem processchambers 106 are configured as UV curing chambers, system 100 can beadapted with one or more of the tandem process chambers havingsupporting chamber hardware as is known to accommodate various otherknown processes such as chemical vapor deposition (CVD), physical vapordeposition (PVD), etch, and the like. For example, system 100 can beconfigured with one of tandem process chambers 106 and a CVD chamber fordepositing materials, such as a low dielectric constant (K) film, on thesubstrates. Such a configuration can maximize research and developmentfabrication utilization and, if desired, eliminate exposure ofas-deposited films to atmosphere.

FIG. 9 is a simplified perspective view of one of tandem processchambers 106 shown in FIG. 8 that is configured for UV curing. Tandemprocess chamber 106 includes a body 200 and a lid 202 that can be hingedto the body 200. Coupled to the lid 200 are two housings 204 that eachinclude inlets 206 along with outlets 208 for passing cooling airthrough an interior of the housings 204. The cooling air can be at roomtemperature or approximately twenty-two degrees Celsius. A centralpressurized air source (not shown) provides a sufficient flow rate ofair to the inlets 206 to insure proper operation of any UV lamp bulbsand/or associated power sources for the bulbs. Outlets 208 receiveexhaust air from the housings 204, which is collected by a commonexhaust system (not shown) that can include a scrubber to remove ozonepotentially generated by the UV bulbs depending on bulb selection. Ozonemanagement issues can be avoided by cooling the lamps with oxygen-freecooling gas (e.g., nitrogen, argon or helium). Details of a coolingmodule that can be used in conjunction with tandem process chamber 106can be found in U.S. application Ser. No. 11/556,642, entitled “NitrogenEnriched Cooling Air Module for UV Curing System,” filed on Nov. 3, 2006and assigned to Applied Materials, the assignee of the presentapplication. The 11/556,642 application is hereby incorporated byreference in its entirety.

Each housing 204 includes an upper housing 210 in which a UV lamp, suchas lamp 32, is placed and a lower housing 214 in which secondaryreflector 40 is placed. Some embodiments of the invention furtherinclude a disc 212 having a plurality of teeth 212 a that grip acorresponding belt (not shown in FIG. 9) that couples the disc to aspindle 216 which in turn is operatively coupled to a motor (not shown).The combination of discs 212, belts, spindle 216 and motor allow upperhousings 210 (and the UV lamps mounted therein) to be rotated relativeto a substrate positioned on a substrate support below lid 202.

As shown in FIG. 10, which is an upward looking perspective view of areflector 40 and a disc 212, each secondary reflector 40 is attached tothe bottom of respective disc 212 by brackets 220 mounted to the outersurface of parts 40 s and 40 c via screw holes 218 (also shown in FIG.2B). This allows secondary reflector to rotate within lower housing 214along with the upper housing and UV lamps. Rotating the UV lamp relativeto the substrate being exposed improves the uniformity of exposureacross the surface of the substrate. In one embodiment, the UV lamp canbe rotated at least 180 degrees relative to the substrate being exposed.In other embodiments the UV lamp can be rotated 270 degrees, a full 360degrees or more.

As already described, in some embodiments the primary and secondaryreflectors are designed to generate high and low irradiance areas thatcompensate for each other during rotation thereby providing a uniformradiation pattern. For example, FIG. 11A graphically depicts theirradiance of a UV lamp module 30 according to one embodiment of theinvention. In this embodiment, the UV lamp, primary reflector andsecondary reflector combine to generate an irradiation pattern thatincludes areas 66 of relatively higher intensity (about 950-1100 W/m²)and areas 68 of relatively lower intensity (approximately 500-700 W/m²)along opposing ends of the outer periphery of the flood patterngenerated by module 30. A large area 67 of relative medium intensity(about 800-900 W/m²) is distributed across most of the area of thesubstrate being exposed. Higher intensity areas 66 are positioned insubstantially the same annular region as lower intensity areas 68 andcan be said to be positioned at respective corners of an imaginarysquare formed within the circular flood pattern.

FIG. 11B depicts actual radiation levels shown in FIG. 11A along both ahorizontal axis 69 and vertical axis 70. FIG. 11B shows thecomplimentary effect of areas 67 and 68 within annular region 71 andalso shows that the variation in irradiance along the different axis inthe central region of the substrate is greatly reduced as compared tothe variance along the periphery of the substrate.

When UV lamp module 30 is appropriately rotated, the areas of relativelylow and high irradiance depicted in FIG. 11A average out close to themedium irradiance level corresponding to area 67 experienced by themajority of a substrate. FIG. 11C graphically depicts the irradiancepattern of FIG. 11A when rotated 180 degrees during UV exposureaccording to an embodiment of the invention, while FIG. 11D depictsactual radiation levels shown in FIG. 11C along axis 86. The datadepicted in FIGS. 11C and 11D was collected after exposing a substrateto UV radiation under the same conditions as done in FIGS. 11A and 11Bexcept that the UV lamp was rotated 180 degrees during the period ofexposure measured in FIGS. 11C and 1D. As evident from FIGS. 11C and11D, rotating the UV lamp during exposure resulted in exposing thesubstrate to a substantially uniform irradiance level across its entiresurface.

A number of different techniques can be used to rotate the UV lampmodule relative to the substrate. In some embodiments the UV lamp can beheld in a fixed position while the substrate is placed on a substratesupport that rotates. In other embodiments the UV lamp can be rotatedwhile the substrate remains stationary and in still other embodimentsboth the UV lamp and substrate can be rotated, for example in oppositedirections.

FIG. 12A depicts one particular embodiment where two discs 250 a and 250b are shown that are similar to discs 212 depicted in FIG. 9. Belts 252a and 252 b are operatively coupled to each respective disc 250 a and250 b and a spindle 254. While not shown in FIG. 12A, belt 252 a wouldbe positioned on spindle 254 in a different vertical plan than belt 252b. For example, spindle 254 may include two groves, one above the other,through which each respective belt is run. Similarly, each of discs 250a and 250 b may include a grove around its periphery for the belt torun. In other embodiments, discs 250 a, 250 b and spindle 254 include aplurality of teeth around the outer periphery of each that mate to aplurality of teeth formed on the belts 252 a, 252 b as shown in FIG. 9.Also shown in FIG. 12A are guides 256 a-256 d that help maintain propertension on the belts. The single spindle 254 shown in FIG. 12A allowsboth discs 25 a and 250 b to be rotated by the same motor. UV lamps andsecondary reflectors can be attached to discs 250 a, 250 b describedwith respect to FIG. 10. Note that for ease of illustration discs 250 a,250 b are shown as a single solid disc where in actual use inembodiments where the discs are positioned between the UV lamp andsubstrate the discs will have a window or opening (not shown) thatallows UV radiation to pass from through the disc from the UV lamp tothe substrate. In embodiments were discs or similar drive mechanisms arelocated above the UV lamp such windows are not necessary.

FIG. 12B depicts another arrangement that employs separate spindles 254a and 254 b dedicated for the rotation of each of discs 250 a, 250 brespectively. If each spindle is operatively coupled to a separatemotor, this arrangement allows the discs to be rotated independent ofeach other which may be useful, for example, if process requirementsrequire different curing times or rotational speeds in the chambersserved by the UV lamps associated with each of discs 250 a, 250 b. FIG.12C depicts still another embodiment where a single belt 252 loopsaround the periphery of each of discs 250 a and 250 b driven by a singlespindle 254 c. While FIGS. 12A-C depict three specific arrangements toeffect rotation of the UV lamp relative to the substrate, a person ofordinary skill in the art will recognize that a variety of otherarrangements can be employed. Also, a person of skill in the art willappreciate that each of the arrangements illustrated in FIGS. 12A-12C issuitable for rotating UV lamps associated with a tandem process chamber,such as chamber 106 in FIG. 8. Other embodiments of the invention employmotor driven systems that rotate a single UV lamp for a single chambertool.

Reference is now made to FIG. 13, which is a simplified cross-sectionalview (except for the upper portion of the right chamber) of the tandemprocess chamber 106 illustrated in FIG. 8. FIG. 13 shows a partialsection view of tandem process chamber 106 with the lid 202 and housings204. Each of the housings 204 cover a respective one of two UV lampbulbs 302 disposed respectively above two process regions 300 definedwithin the body 200. Each of process regions 300 includes a heatedpedestal 306 for supporting a substrate 308 within the process regions300 during the UV exposure process. Pedestals 306 can be made fromceramic or metal such as aluminum. In one embodiment, the pedestals 306couple to stems 310 that extend through a bottom of the body 200 and areoperated by drive systems 312 to move the pedestals 306 in theprocessing regions 300 toward and away from UV lamp bulbs 302. In someembodiments the drive systems 312 can rotate and/or translate thepedestals 306 during curing to further enhance uniformity of substrateillumination. Adjustable positioning of the pedestals 306 enablescontrol of volatile cure by-product and purge and clean gas flowpatterns and residence times in addition to potential fine tuning ofincident UV irradiance levels on the substrate 308 depending on thenature of the light delivery system design considerations such as focallength.

In general, embodiments of the invention contemplate any UV source suchas mercury microwave arc lamps, pulsed xenon flash lamps orhigh-efficiency UV light emitting diode arrays. The UV lamp bulbs 302are sealed plasma bulbs filled with one or more gases such as xenon (Xe)or mercury (Hg) for excitation by power sources (not shown). Preferably,the power sources are microwave generators that can include one or moremagnetrons (not shown) and one or more transformers (not shown) toenergize filaments of the magnetrons. In one embodiment having kilowattmicrowave (MW) power sources, each of the housings 204 includes anaperture adjacent the power sources to receive up to about 6000 W ofmicrowave power from the power sources to subsequently generate up toabout 100 W of UV light from each of the bulbs 302. In anotherembodiment, the UV lamp bulbs 302 can include an electrode or filamenttherein such that the power sources represent circuitry and/or currentsupplies, such as direct current (DC) or pulsed DC, to the electrode.

The power sources for some embodiments can include radio frequency (RF)energy sources that are capable of excitation of the gases within the UVlamp bulbs 302. The configuration of the RF excitation in the bulb canbe capacitive or inductive. An inductively coupled plasma (ICP) bulb canbe used to efficiently increase bulb brilliancy by generation of denserplasma than with the capacitively coupled discharge. In addition, theICP lamp eliminates degradation of UV output due to electrodedegradation resulting in a longer-life bulb for enhanced systemproductivity. Benefits of the power sources being RF energy sourcesinclude an increase in efficiency.

Preferably, the bulbs 302 emit light across a broad band of wavelengthsfrom 180 nm to 400 nm. The gases selected for use within the bulbs 302can determine the wavelengths emitted. Since shorter wavelengths tend togenerate ozone when oxygen is present, UV light emitted by the bulbs 302in some embodiments is tuned to predominantly generate broadband UVlight above 200 nm to avoid ozone generation during cure processes.

UV light emitted from the UV lamp bulbs 302 enters the processingregions 300 by passing through windows 314 disposed in apertures in thelid 202. In one embodiment the windows 314 are made of an OH freesynthetic quartz glass and have sufficient thickness to maintain vacuumwithout cracking. Further in one embodiment, the windows 314 are fusedsilica that transmits UV light down the approximately 150 nm. Since thelid 202 seals to the body 200 and the windows 314 are sealed to the lid202, the processing regions 300 provide volumes capable of maintainingpressures from approximately 1 Torr to approximately 650 Torr.Processing or cleaning gases enter the process regions 300 via arespective one of two inlet passages 316. The processing or cleaninggases then exit the process regions 300 via a common outlet port 318.Additionally, the cooling air supplied to the interior of the housings204 circulates past the bulbs 302, but is isolated from the processregions 300 by the windows 314.

During UV curing it is common for water molecules and various otherspecies to be outgassed or otherwise released from the film or materialbeing cured or processed. These species tend to collect on variousexposed surfaces of the chamber, such as windows 314, and can reduce theefficiency of the process. To reduce the build-up of these species andmaintain a high efficiency process, periodic cleaning of the surfaces,such as after every 200 wafers, may be employed as described below.Also, a laminar flow of a purge gas, such as argon or another noble orinert gas or other suitable gas, may be provided across the irradiatedsurface of the substrate being treated to carry outgassed species out ofthe chamber. The laminar flow may emanate from a pump liner (not shown)operatively coupled to inlet and outlet ports 316, 318. Details of aprocessing region 300 having such a pump liner are in U.S. applicationSer. No. 11/562,043, entitled “Increased Tool Utilization/Reduction inMWBC for UV Curing Chamber,”, filed on Nov. 21, 2006 and assigned toApplied Materials, Inc., the assignee of the present application. TheSer. No. 11/562,043 application is hereby incorporated by reference inits entirety.

UV lamp bulbs 302 can also be activated during chamber clean processesto increase the efficiency of the chamber clean. As an example cleanprocess, the temperature of the pedestals 306 can be raised to betweenabout 100° C. and about 600° C., preferably about 400° C. With the UVpressure in the processing regions 300 elevated by the introduction ofthe cleaning gas into the region through the inlet passages 316, thishigher pressure facilitates heat transfer and enhances the cleaningoperation. Additionally, ozone generated remotely using methods such asdielectric barrier/corona discharge or UV activation can be introducedinto the processing regions 300. The ozone dissociates into O⁻ and O₂upon contact with the pedestals 306 that are heated. In the cleanprocess, elemental oxygen reacts with hydrocarbons and carbon speciesthat are present on the surfaces of the processing regions 300 to formcarbon monoxide and carbon dioxide that can be pumped out or exhaustedthrough the outlet port 318. Heating the pedestals 306 while controllingthe pedestal spacing, clean gas flow rate, and pressure enhances thereaction rate between elemental oxygen and the contaminants. Theresultant volatile reactants and contaminants are pumped out of theprocessing regions 300 to complete the clean process.

In order to increase the irradiation generated by the UV lamp (e.g., UVlamp module 30) and thus allow for shorter exposure times and higherwafer throughput, some embodiments of the invention employ multiple UVlamps for each single wafer processing region. FIG. 14 is a simplifiedcross-sectional view of a two UV source, single wafer UV cure chamber400 according to one embodiment of the invention. In FIG. 14, twocylindrical high power mercury microwave lamps 410 and 412 arepositioned parallel to each other within respective resonant cavities402 and 404. Lamp 410 includes an elongated UV bulb 414 partiallysurrounded by a non-focal elliptical primary reflector having an outerreflector 420 and inner reflector 422. Lamp 412 includes an elongated UVbulb 416 partially surrounded by a non-focal elliptical primaryreflector having an inner reflector 424 and an outer reflector 426.Slits 430 and 432 between the inner and outer primary reflectors of eachlamp 410, 412 allow for lamp cooling air introduced through inlets 406to flow across bulbs 414 and 416.

An aluminum secondary reflector 440 is positioned between lamps 410, 412and a quartz window 448 on the atmospheric side of the window. Asubstrate 450 is located on a vacuum side of quartz window 448 andpositioned on a heated substrate support (not shown) within a processingregion such as region 300 within a pressure controlled chamber asdescribed with respect to FIG. 13. Substrate 448 can be located about5-20 inches away (6-11 inches away in another embodiment) from lamps410, 412. An opening 442 on the upper portion of the secondary reflectorallows lamp cooling air to exit with minimum conductance loses. All ofthe primary and secondary reflectors have a dichroic coating on theirreflective surfaces to ensure maximum reflectivity in the 180-400 nmrange. As shown in FIG. 15 in this particular two lamp configuration,the housing associated with lamps 410 and 412 extends beyond the outlineof substrate 450.

Each lamp, with its associated primary reflectors, delivers UV radiationto approximately one half of the wafer. The direct radiation(non-reflected) that contacts the substrate has a higher intensity nearthe center of the wafer than at the wafer's edge. In order to compensatefor this, light reflected from the reflectors is focused on the edge ofthe wafer. To this end, the inner and outer primary reflectors of eachof lamps 410 and 412 have different curvatures such that the primaryreflectors of each lamp produce an asymmetric irradiance profile inwhich the lowest irradiance is in the center of the wafer and thehighest irradiance is at the edge of the wafer (in this embodiment outerreflectors 420 and 426 are symmetric to each other as are innerreflectors 422 and 424). FIG. 16 shows the irradiance pattern of theinner and outer primary reflectors 424, 426 for UV lamp 412. As shown inFIG. 16, outer primary reflector 426 produces irradiance profile 460having an area of highest intensity towards the center of the substratewhile inner primary reflector 424 produces irradiance profile 462 havingan area of highest intensity along the periphery of the substrate.Irradiance profiles 460 and 462 combine to produce a combined irradianceprofile 464 that covers approximately one half of substrate 450 and hasan area 466 of highest intensity along the periphery of the substrate.Each of profiles 460, 462 and 464 is taken along diameter A-A′ shown inFIG. 16.

FIG. 17 shows the irradiance profile produced by lamp 410 combined withlamp 412 (including bulbs 414, 416 and primary reflectors 420, 422, 424and 426). As shown in FIG. 17, the lamps produce a convex irradianceprofile 467A along the lamp axis and a concave irradiance profile 467Bacross the lamp axis. The curvature of the primary reflectors is suchthat static irradiance profile 468 (profiles 467A and 467B combined) hasa “Batman” shape as viewed along and across lamp axis B-B′. Oncerotated, however, the complimentary areas of high intensity and lowintensity combine to generate a significantly more uniform profile asshown by 470.

Without any reflectors, approximately 15% of direct light emitted by thetwo mercury lamps would reach the surface of substrate 450. Theirradiance profile of the direct light is a center high dome. Theprimary reflectors (420,422) and (424,426) approximately triple theamount of light reaching the substrate. As evident from an analysis ofFIGS. 17 and 18, secondary reflector 440 increases the irradiance byabout an additional 35% by redirecting the light that would otherwisefall outside the substrate back to the substrate surface. Specificcurvature of the reflective surface of the secondary reflector allowsfurther correction to irradiance profile as described above. Thistechnique is especially useful in achieving a flat irradiance profile atthe edge of the wafer without excessive losses to light irradiance. FIG.18 shows the affect the addition of secondary reflector 440 has to theirradiance profile generated by just the lamps and primary reflectors.As shown in FIG. 18, irradiance profile 472 has a similar “batman” shapeas profile 468 but at a significantly higher intensity level.Furthermore, secondary reflector 440 enables irradiance pattern 474 tobe generated such that, when rotated, irradiance profile 476 is evenmore uniform than profile 470.

In one particular embodiment of the invention, lamps 410 and 412 arelinear lamps inside a rectangular footprint that deliver light to a 12″wafer with minimum losses and light irradiance non-uniformity below 3%.The optical system (lamp, primary and secondary reflectors) of curechamber 400 are designed to take full advantage of lamp rotation. Asshown in FIG. 18, the lamps and reflectors combine to generate a concaveirradiance profile across the lamps and a convex irradiance profilealong the lamps. Then, after rotation high and low irradiance areascompensate each other producing relatively flat profile. Each lampproduces an asymmetric profile because each lamp covers approximatelyhalf of the wafer, therefore the internal primary reflector and externalprimary reflector of each lamp have a different shape. Also, the primaryreflectors have a non-focused elliptical curvature, without localextremities, which makes them less sensitive to manufacturing accuracyand alignment accuracy.

The second component of the optical system is a secondary reflector 440.Secondary aluminum reflector (440) serves two functions. First, itincreases the average irradiance on the wafer (in one specificembodiment by about 35%) by reducing the light falling outside thewafer. Second, the secondary reflector allows further improvement toirradiance uniformity across wafer. In some embodiments a finalcorrection to irradiance profile (correction based on actual filmshrinkage map) can also be done by shape modification of the secondaryreflector. Both primary and secondary reflectors have dichroic coatingto allow at least 90% reflectance in the 200 nm-400 nm range.

As shown in Table 1 below, tests run by the inventors demonstrate thatembodiments of the invention that use the two lamp rotational techniquedepicted in FIG. 14 allowed a reduction in cure time for a low-k filmfrom 25 minutes, for stationary single lamp, to 9 minutes with the sameaverage film shrinkage and significantly improved film shrinkageuniformity.

TABLE 1 Station- Single Dual Unit ary Rotating Rotating Lamp Distancefrom inch 10.66″ 10.8″ 8.8″ Wafer Lamp Power W 90 W 90 W 90 W + 90 WIrradiance: Average on W/m{circumflex over ( )}2 368 616 1023 Wafer¹Irradiance: Unformity¹ % 9.6 5.4 2.6 Irradiance: Range¹ % +/−20 +/−14+/−8 UV Treatment Time² min 25 15 9 Film Shrinkage Non- % 5.6 4.3 3.0uniformity² ¹= simulated result ²= measured result

FIG. 19 is a simplified cross-sectional view of another embodiment of adual lamp system 480 according to the present invention. System 480 issimilar to system 400 shown in FIG. 14 except that first and second UVlamps 482, 484 are mounted at opposing angles to each other in order toallow the lamps to be positioned closer to the center of the substratebeing treated and allow more room for cooling air to flow through thelamps. In some embodiments, the opposing angles are between 2-25 degreesrelative to vertical and between 4-10 degrees in other embodiments.Other configurations of lamps can be used in additional embodiments ofthe invention. In system 480 shown in FIG. 19, the design of the primaryand secondary reflectors can be tailored using the techniques describedabove to compensate for the angle of lamps 482 and 484 to produce adesired irradiance pattern.

The efficiency of UV lamps, such as lamps 410, 412, deteriorate overtime. Some embodiments of the invention include irradiance sensors thatallow the intensity/reflectivity of each component of the UV lamp to bemonitored separately in order to determine a replacement schedule andattain high light uniformity over the lifetime of the lamp. To achievethis function, one embodiment of the invention includes a plurality ofholes or slots (sometimes referred to herein as light pipes) createdthrough the secondary reflector. Radiation passing through each lightpipe contacts a UV radiation sensor that measures the intensity ofradiation in a selected wavelength range (e.g., 200-400 nm or a narrowerrange such as 250-260 nm, 280-320 nm, 320-390 nm or 395-445 nm) passingthrough the light pipe.

The location and direction of the light pipe, its diameter and itslength determine which individual light rays generated from a lamp makeit through the light pipe to reach the sensor (i.e., the acceptanceangle of the light pipe). Each light pipe is designed to for a specificacceptance angle that allows one lamp component (e.g., one lamp bulb orone primary reflector) to be monitored independent of the othercomponents. Generally, the axis of the light pipe is coincident with theangle rays that are intended to pass through the pipe. This way onlylight generated by or reflected from the desired component passesthrough the light pipe to the sensor. A light pipe may thus beconsidered a directional filter that allows only rays from a particulardirection to be passed through the filter.

Depending on the thickness of the secondary reflector in the region anindividual light pipe is formed, the length of the light pipe may beextended by inserting a tube (e.g., an aluminum tube) into the hole orslot formed through the secondary reflector. To reduce the effects ofreflectance within the light pipe and ensure that only radiation rayswithin the particular angle of acceptance a light pipe is designed forreach its sensor, the interior surfaces of a light pipe may be lined orcoated with an appropriate light absorbing material that absorbsradiation in the wavelengths for which the sensor detects.Alternatively, the interior surface of a light pipe may be treated tohave a high roughened (e.g., by scrubbing with a steel brush) todissipate, via multiple reflections, unwanted light that contacts thewall of the light pipe.

In monitoring an individual component of a UV lamp, it is desirable thatthe light pipe allow only rays generated by or reflected by thatcomponent to reach the sensor at the end of the light pipe that monitorsthe component. In some instances it may not be practical to design thelight pipe such that 100% of the rays reaching its associated sensor arefrom a single component and instead the light pipe is designed so that asuitably high percentage, e.g., 80% or 90%, of the rays that reach itssensor are from the monitored component.

For the UV cure system of FIG. 14, six different light pipes can beincluded to separately monitor each of UV bulbs 414 and 416 as well aseach of the primary reflectors 420, 422, 424 and 426. Direct rays andreflected rays travel at different angles. Similarly, reflected raysfrom each of the primary reflectors 420, 422, 424 and 426 land ondifferent spots of the secondary reflector. Using this knowledge and anappropriate ray tracing program, a location of each light pipe throughthe secondary reflector can be determined that allows each light pipe tomonitor one of components.

Reference is now made to FIGS. 20 and 21 which are perspective views ofsecondary reflector 440 previously shown in FIG. 14 prior to andsubsequent to the incorporation of light pipes in the secondaryreflector. FIG. 20 shows locations 501-506 in secondary reflector 440 atwhich the six light pipes to monitor the separate components (bulbs 414,416 and primary reflectors 420, 422, 424, 426) can be positioned.Locations 501A and 502A are on opposing ends of the secondary reflectorand are well suited for light pipes that are designed to filter out allor most of the radiation reflected from the primary reflectors therebyallowing only direct radiation from one of bulbs 414 or 416 to passthrough. When the UV lamp 410 is positioned over the left hand portionof secondary reflector 440 as it is laid out in FIG. 20 and UV lamp 412is positioned over the right hand side of the secondary reflector, alight pipe to monitor direct radiation generated by UV bulb 414 can beplaced at location 501A and a light pipe to monitor direct radiation byUV bulb 416 can be placed at location 502A. Locations 50B and 502B arealternative locations at which light pipes may be placed to monitor UVbulbs 414 and 416, respectively. Additionally, a light pipe to monitorradiation reflected by outer primary reflector 420 can be place atlocation 503, a light pipe to measure radiation reflected by innerprimary reflector 422 can be place at location 504, a light pipe tomonitor radiation reflected by inner primary reflector 424 can be placeat location 505 and a light pipe to measure radiation reflected by outerprimary reflector 426 can be place at location 506.

FIG. 21 shows light pipes 510-513 that have been incorporated intosecondary reflector 440 at locations 503-506, respectively and lightpipes 514 and 515 formed at locations 501 b and 502 b, respectively.Light pipe 510 monitors the reflectance of outer primary reflector 420,pipe 511 monitors the reflectance of inner primary reflector 422, pipe512 monitors the reflectance of inner primary reflector 424 and pipe 513monitors the reflectance of outer primary reflector 426. Light pipes 510and 513 are formed from openings through the reflective surface of thesecondary reflector in locations 503 and 506, respectively. Light pipes511 and 512 are formed from openings through the reflective surface ofthe secondary reflector in locations 504 and 505 respectively.Additionally, an extension tube is fitted to each of the holes inlocations 504 and 505 to lengthen each light pipe 511 and 512 to furtherfilter out radiation that is not associated with the reflector each pipeis associated with. Light pipes 514 and 515, which are also fitted withextension tubes, monitor the intensity of UV bulbs 414 and 416,respectively.

Some embodiments of the invention include a separate UV radiation sensorat the end of each light pipe. Embodiments of the invention that rotateone or more of the UV lamp or substrate during the cure process,however, may use fewer than one sensor per light pipe. For example, inan embodiment where the lamp module is rotated 180 degrees during the UVcure process, two UV radiation sensors can be used. A first sensor maybe positioned, for example, to detect radiation passing through lightpipes 510, 514 and 512 while a second sensor may be positioned to detectradiation passing through light pipes 511, 515, 513. In another example,a single sensor may be used to detect radiation passing through each oflight pipes 510-515 providing the lamp module is rotated a sufficientamount (e.g., 270 or 360 degrees) to allow light passing through each ofthe light pipes to contact the sensor during the cure process. Whereindividual sensors monitor multiple light pipes, logic or controlcircuitry (e.g., a microcontroller or computer processor) tracks thetiming of the rotations and the data samples from the sensor and usesthe timing information and the known rotational pattern to determinewhich light pipe individual sensor readings are associated with.

In order to reduce noise detected by a UV radiation sensor, it isdesirable that the sensor be placed as close a possible to the exit ofthe light pipes. In an embodiment where a single sensor is used todetect UV radiation emitted through multiple light pipes, this mayrequire extending the length of certain light pipes relative to othersto ensure that all light pipes operatively positioned to work with aparticular sensor have a similar distance between the end of the lightpipe and the sensor. As an example, reference is made to FIGS. 22A and22B, which are perspective views of one side of a reflector 540according to one embodiment of the invention. Reflector 540 includeslight pipes 610, 612 and 614 formed in regions of the reflectorcomparable to the regions at which light pipes 510, 512 and 514 areformed in reflector 440. Reflector 540 is notably thicker than reflector440, however, in an outer peripheral region 545 of the reflector. Region545 includes a curved surface 550 that has a curvature radius selectedso that the end of each of light pipes 510, 512 and 514 is equallyspaced to a sensor (not shown) that is operatively positioned to detectUV radiation passing through each of the holes as secondary reflector540 is rotated.

Having fully described several embodiments of the present invention,many other equivalent or alternative apparatuses and methods of curingdielectric films according to the present invention will be apparent tothose skilled in the art. These alternatives and equivalents areintended to be included within the scope of the present invention.

1. A substrate processing tool comprising: a body defining a substrateprocessing region; a substrate support adapted to support a substratewithin the substrate processing region; an ultraviolet (UV) radiationlamp spaced apart from the substrate support and configured to generateand transmit ultraviolet radiation to a substrate positioned on thesubstrate support, the UV radiation lamp comprising a source of UVradiation and a primary reflector partially surrounding the source of UVradiation, the primary reflector having the primary reflector having areflective surface that includes at least one parabolic section and atleast one elliptical section; and a secondary reflector positionedbetween the primary reflector and the substrate support, wherein thesecondary reflector alters a substantially rectangular irradiancepattern generated by the UV radiation lamp and primary reflector tocreate a substantially circular flood pattern.
 2. The substrateprocessing tool of claim 1 wherein the primary reflector includes aplurality of elliptical sections including first, second and thirdelliptical sections positioned adjacent to each other and configured toreflect radiation towards a common area of the substrate support.
 3. Thesubstrate processing tool of claim 2 wherein the source of UV radiationis an elongated UV bulb.
 4. The substrate processing tool of claim 3wherein the parabolic section of each reflective panel is located in aportion of the panel closer to the UV bulb than the portion of the panelin which the elliptical section is located.
 5. The substrate processingtool of claim 2 wherein each of the plurality of elliptical sections hasa curvature without a focal point.
 6. The substrate processing tool ofclaim 5 wherein the at least one parabolic section reflects rays thatare not parallel to each other.
 7. The substrate processing tool ofclaim 2 wherein the reflective surfaces of the inner and outer opposingpanels are asymmetrically shaped with respect to each other.